TWO-BINDER-ACTIVATED, CALANDRED SEMI-DRY ELECTRODE

Abstract

A battery cell contains A anode electrodes, C cathode electrodes, and S separators, where C, A, and S are integers greater than one. Each C cathode electrode contains a cathode current collector and a cathode active material layer arranged on the cathode current collector. The cathode active material layer comprises a cathode active material, a conductive filler, and a binder containing a fibrillating binder and a copolymer, including polyacrylonitrile (PAN) and polyacrylic acid (PAA).

Description

INTRODUCTION

[0001] The information contained in this section serves to present the general context of the disclosure. Works of the inventors mentioned herein, insofar as they are described in this section, as well as aspects of the description that might not otherwise be considered prior art at the time of filing, are neither expressly nor implicitly admitted as prior art against the present disclosure.

[0002] The present disclosure relates to battery cells and in particular to a cathode electrode with a cathode active material layer comprising cathode active material, a conductive filler and a dual binder with a fibrillating binder and a copolymer.

[0003] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, comprise one or more electric motors and a battery system with one or more battery cells, modules, and / or packs. A power control system is used to manage the charging and / or discharging process of the battery system during charging and / or driving.

[0004] Battery cells contain cathode electrodes, anode electrodes, and separators. The cathode electrodes contain a layer of active cathode material (containing cathode active material) arranged on a cathode current collector.

[0005] The anode electrodes contain an anode active material layer (containing anode active material) that is arranged on an anode current collector.

[0006] Known battery cells are described, for example, in EP 3 940 817 B1 and DE 10 2021 113 544 A1. SUMMARY

[0007] According to the invention, a battery cell comprises A anode electrodes, C cathode electrodes, and S separators, wherein C, A, and S are integers greater than one. Each of the C cathode electrodes comprises a cathode current collector and a cathode active material layer arranged on the cathode current collector. The cathode active material layer comprises a cathode active material, a conductive filler, and a binder containing a fibrillating binder and a copolymer, including polyacrylonitrile (PAN) and polyacrylic acid (PAA), wherein the porosity of the cathode active material layer is in the range of 25% to 35%.

[0008] In other cases, the cathode active material layer comprises the cathode active material in a range of 84 wt.% to 98.7 wt.%, the conductive filler in a range of 0.5 wt.% to 10 wt.%, the fibrillating binder in a range of 0.5 wt.% to 5 wt.%, and the copolymer in a range of 0.1 wt.% to 1.5 wt.%.

[0009] In other cases, the cathode active material comprises a material selected from a group consisting of NCM, NCMA, NMx, LFP, LMFP, and combinations thereof. The fibrillating binder contains polytetrafluoroethylene (PTFE).

[0010] In other cases, the hydrogen in a carboxyl (COOH) of the PAA is at least partially replaced by a lithium ion through reaction with a lithium-based chemical to form PAA Li x H 1-x(0 < x < 1). The hydrogen in a carboxyl (COOH) of PAA is at least partially replaced by sodium ions through reaction with a sodium-based chemical to form PAA Na. x H 1-x to form (0 < x < 1).

[0011] In other cases, the density of the cathode active material ranges from 1.0 to 3.7 g / cm³. 3 The cathode active material layer is attached to the cathode current collector without the use of a conductive adhesive.

[0012] In other cases, the conductive filler includes a carbon-based conductive filler selected from a group consisting of carbon black, graphite, graphene, graphene oxide, Super P, acetylene black, Ketjen black (KB), single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), carbon nanotubes, and combinations thereof. The conductive filler includes a non-carbon-based conductive filler selected from a group consisting of a simple oxide, a superconducting oxide, a carbide, a silicide, and combinations thereof.

[0013] A battery cell is also described according to the invention, comprising A anode electrodes, C cathode electrodes, and S separators, where C, A, and S are integers greater than one. Each C cathode electrode comprises a cathode current collector and a cathode active material layer arranged on the cathode current collector. The cathode active material layer comprises a cathode active material selected from the group consisting of NCM, NCMA, NMx, LFP, LMFP, and combinations thereof, a conductive filler, and a binder containing polytetrafluoroethylene (PTFE) and a copolymer with polyacrylonitrile (PAN) and polyacrylic acid (PAA). The cathode active material layer is attached to the cathode current collector without the use of a conductive adhesive.

[0014] In other cases, the cathode active material layer comprises the cathode active material in a range of 84 wt.% to 98.7 wt.%, the conductive filler in a range of 0.5 wt.% to 10 wt.%, the PTFE in a range of 0.5 wt.% to 5 wt.%, and the copolymer in a range of 0.1 wt.% to 1.5 wt.%.

[0015] In other cases, the hydrogen in a carboxyl (COOH) of the PAA is at least partially replaced by a lithium ion through reaction with a lithium-based chemical to form PAA Li x H 1-x (0 < x < 1). The hydrogen in a carboxyl (COOH) of PAA is at least partially replaced by sodium ions through reaction with a sodium-based chemical to form PAA Na. x H 1-x to form (0 < x < 1).

[0016] In other cases, the porosity of the cathode-active material layer ranges from 20% to 60%. A cathode-active material layer porosity ranges from 25% to 35%. A compaction density ranges from 1.0 to 3.7 g / cm³. 3 .

[0017] Further applications of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples serve only for illustration and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present disclosure is better understood from the detailed description and the accompanying drawings; the following applies: Fig. Figure 1 is a lateral cross-section of an example of a battery cell with C cathode electrodes, A anode electrodes and S separators according to the present disclosure; Fig. Figure 2 is a lateral cross-section of an example of a cathode electrode according to the present disclosure; Fig. Figure 3 is a lateral cross-section of an example of an anode electrode according to the present disclosure; Fig. Figure 4 is a diagram showing an example of the adhesive force for separating the cathode active material layer from the cathode current collector according to the present disclosure; Fig. 5 is a diagram showing an example of the voltage as a function of the capacity for half-button cells according to the present disclosure; and Fig. Figure 6 is a diagram showing an example of the discharge capacity as a function of cycles for half-button cells according to the present disclosure.

[0019] Reference numbers can be used repeatedly in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0020] Although the battery cells shown in the present disclosure are in connection with electric vehicles, the battery cells can be used in stationary applications and / or other applications.

[0021] A freestanding cathode active material layer based on polytetrafluoroethylene (PTFE) as a binder can be produced using a roll-to-roll process. The freestanding cathode active material layer can be oven-dried and then laminated onto a current collector using intaglio printing and a liquid conductive adhesive. After intaglio printing, the cathode electrode is oven-dried and then collected on a roll. Manufacturing costs are high due to the use of intaglio printing and a recovery system, which may be required during both lamination and drying (e.g., when using lithium-ion phosphate (LFP) as the cathode active material). After bonding, the cathode active material layer exhibits a 180° peel strength of 140 N / m.

[0022] The present disclosure relates to a cathode electrode with a cathode active material layer comprising a cathode active material (e.g., LFP or another active material), a conductive filler, and a dual binder system with a fibrillating binder and a copolymer of polyacrylonitrile (PAN) and polyacrylic acid (PAA) (e.g., PAN-PAA copolymer). The cathode active material layer is produced as a free-standing film and then calendered directly onto a current collector without the use of a gravure printing process or conductive adhesive.

[0023] In some examples, the fibrillating binder contains polytetrafluoroethylene (PTFE). In some examples, the cathode active layer contains PTFE in a range of 0.5 wt% to 5 wt%. In some examples, the cathode active layer contains the PAN-PAA copolymer in a range of 0.1 wt% to 1.5 wt%.

[0024] The fibrillated PTFE binder is used to encapsulate active material particles and build a 3D bonding network within the freestanding film. The PAN-PAA polymer features custom-designed functional groups to generate robust adhesion between the freestanding film and the current collector using a warm / hot calendering process. In some examples, the warm process temperature ranges from 20°C to 50°C, while in others, the hot process temperature ranges from 50°C to 200°C.

[0025] With the following reference to Fig. 1 contains a battery cell 10, cathode electrodes 20, anode electrodes 40, and separators 32, which are arranged in a predetermined order in a battery cell stack 12, where C, S, and A are integers greater than zero. The battery cell stack 12 is arranged in a housing 50. Liquid electrolyte 52 is filled into the housing 50.

[0026] The C cathode electrodes 20-1, 20-2, ... and 20-C contain a cathode active material layer 24, which is arranged on one or both sides of a cathode current collector 26. The A anode electrodes 40-1, 40-2, ... and 40-A contain anode active material layers 42, which are arranged on one or both sides of the anode current collectors 46. The S separators 32-1, 32-2, ..., and 32-S are arranged between the C cathode electrodes 20 and the A anode electrodes 40.

[0027] In some examples, the A anode electrodes 40 and the C cathode electrodes 20 exchange lithium ions during charging / discharging. In some examples, the cathode active material layers 24 and / or the anode active material layers 42 comprise coatings that include one or more active materials, one or more conductive fillers, and / or one or more binders, which are cast or applied to one or both sides of the cathode current collector 26 and / or the anode current collector 46.

[0028] In some examples, the cathode current collector 26 and / or the anode current collector 46 comprise metal foil, metal mesh, perforated metal, three-dimensional (3D) metal foam, and / or expanded metal. In some examples, the current collectors are made of one or more materials selected from the group consisting of copper, stainless steel, brass, bronze, zinc, aluminum, and / or their alloys. In some examples, the current collector is coated with carbon. The outer tabs 28 and 48 are connected to the current collectors of the cathode and anode electrodes, respectively, and can be located on the same side or on opposite sides of the battery cell stack 12. The outer tabs 28 and 48 are connected to the terminals of the battery cells.

[0029] With the following reference to Fig. Figure 2 shows one of the C cathode electrodes 20 in more detail. The cathode active material layer 24 contains a cathode active material 62, a conductive filler 64, a first binder 66 containing a fibrillating binder, and a second binder 68 containing the PAN-PAA copolymer.

[0030] In some examples, the cathode active layer comprises the cathode active material in a range of 84 wt% to 98.7 wt%, the conductive filler in a range of 0.5 wt% to 10 wt%, the fibrillating binder in a range of 0.5 wt% to 5 wt%, and the PAN-PAA copolymer in a range of 0.1 wt% to 1.5 wt%. In some examples, the cathode active material comprises lithium nickel cobalt manganese (NCM), lithium nickel cobalt manganese aluminum (NCMA), lithium nickel metal (NMx), lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), and combinations thereof.

[0031] In some examples, the area-specific capacitance of the cathode electrode is in the range of 2.5 to 10 mAh / cm². 2 In some examples, the area-specific capacitance of the cathode electrode is in the range of 3.5 to 4 mAh / cm². 2 In some examples, the area-related capacity fluctuation is in the range of + / - 3%.

[0032] In some examples, the compression density ranges from 1.0 to 3.7 g / cm³. 3 In some examples, the pressing density for LFP ranges from 2.0 to 2.7 g / cm³. 3 with a density variation of + / - 3%. In some examples, the density for NCM ranges from 3.0 to 3.7 g / cm³. 3 with a density variation in the range of + / - 3%. According to the invention, the porosity of the cathode active material layer is in the range of 25% to 35%.

[0033] In some examples, the conductive filler contains a carbon-based conductive filler and / or a non-carbon-based conductive filler. In some examples, the carbon-based conductive filler is selected from a group consisting of carbon black, graphite, graphene, graphene oxide, Super P, acetylene black, Ketjen black (KB), single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), carbon nanotubes, and other electronically conductive fillers. In some examples, the non-carbon-based conductive filler is selected from a group consisting of oxides (e.g., ruthenium oxide (RuO2), tin oxide (SnO2), zinc oxide (ZnO), germanium oxide (Ge2O3), superconducting oxides (e.g., YBa2Cu3O7, La)). 0,75 Approx 0,25 MnO3), carbide (e.g. SiC2), silicide (e.g. MoSi2) and combinations thereof.

[0034] In some examples, the structure of the PAN-PAA copolymer is:

[0035] In some examples, the hydrogen on the carboxyl (COOH) of the PAA is wholly or partially replaced by a lithium ion (Li) through reaction with a lithium-based chemical (e.g., lithium hydroxide (LiOH)). + ) replaced to PAA Li x H 1-x (0 ≤ x ≤ 1). In some examples, the hydrogen on the carboxyl (COOH) of the PAA is wholly or partially replaced by a sodium ion (Na) by reaction with a sodium-based chemical (e.g., sodium hydroxide (NaOH)). + ) replaced to PAA Na x H 1-x to form (0 ≤ x ≤ 1).

[0036] In some examples, the polymers may be in powder form, as a dispersion, or as a solution. In some examples, the solids content for the dispersion or solution ranges from 2 to 25 wt%. In some examples, the solids content for the dispersion or solution ranges from 10 to 20 wt%. In some examples, the PTFE is dispersed in an aqueous solution. In some examples, the PTFE constitutes 10 to 60 wt%. In some examples, the molecular weight of PTFE is greater than 5M.

[0037] With the following reference to Fig. Figure 3 shows one of the anode electrodes 40 in more detail. The anode active material layer 42 contains an anode active material 72, a conductive filler 74, and a binder 76. In some examples, the anode active material 72 is selected from a group consisting of graphite, carbon, silicon-carbon, silicon dioxide (SiO₂). x), lithium-containing silicon dioxide (LSO), a graphite mixture and combinations thereof.

[0038] In one exemplary implementation, a PAN-PAA solution is mixed with a solvent such as glycol. The PAN-PAA and glycol mixture is added to a mixture of the active material, the conductive filler, and the PTFE binder. In some examples, the cathode active material layer contains LFP at 95.5 wt%, the PTFE binder at 2 wt%, the conductive filler SP at 1 wt% and KB at 1 wt%, and the PAA-PAN at 0.5 wt%. A mixture containing the active material, the conductive filler, the PTFE, the PAN-PAA, and the glycol mixture was pressed and heated to form a freestanding film. The freestanding film was then dried in an oven. The dried, free-standing foil was laminated onto the cathode current collector (e.g., a 20 µm thick aluminum foil) by pressing and heating the dried, free-standing foil and the cathode current collector at 25 °C and 500 PSI. No conductive adhesive was used.

[0039] With the following reference to Fig. Figures 4 to 6 show the behavior of the exemplary cathode electrode. Fig. 4. The cathode active material layer required a force of 194 N / m to remove it from the cathode current collector. In Fig. Figure 5 shows the behavior of the first cycle of the cathode electrode (e.g., of a half-button cell) at 25 °C. The operating range of the battery cell was 2.0 V to 3.7 V. Charging was performed with constant current and constant voltage (CCCV) using a C / 50 cone. Fig. Figure 6 shows the discharge capacity as a function of cycles for the half-button cells.

[0040] As will be evident, the battery cells can be manufactured without using the gravure printing process and / or the recovery system, thus reducing costs. The cathode active material layer is attached to the cathode current collector with the same or a higher adhesive force than cathode electrodes manufactured using the gravure printing process.

Claims

[1] Battery cell, comprising: A Anode electrodes; C Cathode electrodes, each containing a cathode current collector and a cathode active material layer arranged on the cathode current collector; and S separators, where C, A and S are integers greater than one; the cathode active material layer comprises: a cathode active material; a conductive filler; and a binder containing a fibrillating binder and a copolymer with polyacrylonitrile (PAN) and polyacrylic acid (PAA), the porosity of the cathode active material layer is in the range of 25% to 35%. [2] Battery cell according to claim 1, wherein the cathode active material layer comprises: the cathode active material in a range of 84 wt.% to 98.7 wt.%, the conductive filler in a range of 0.5 to 10 wt.%, the fibrillating binder in a range of 0.5 wt.% to 5 wt.%, and the copolymer in a range of 0.1 wt.% to 1.5 wt.%. [3] Battery cell according to claim 1, wherein the cathode active material comprises a material selected from the group consisting of NCM, NCMA, NMx, LFP, LMFP and combinations thereof. [4] Battery cell according to claim 1, wherein the fibrillating binder contains polytetrafluoroethylene (PTFE). [5] Battery cell according to claim 1, wherein hydrogen in a carboxyl (COOH) of the PAA is at least partially replaced by a lithium ion by reaction with a lithium-based chemical to form PAA Li x H 1-x to form (0 ≤ x ≤ 1). [6] Battery cell according to claim 1, wherein hydrogen in a carboxyl (COOH) of the PAA is at least partially substituted by sodium ions by reaction with a sodium-based chemical to form PAA Na x H 1-xto form (0 ≤ x ≤ 1). [7] Battery cell according to claim 1, wherein the density of the cathode active material is in a range of 1.0 to 3.7 g / cm³ 3 lies. [8] Battery cell according to claim 1, wherein the cathode active material layer is attached to the cathode current collector without the use of a conductive adhesive.

Images